Drilling fluids serve many functions during drilling, one of which is to remove excavated rock, or “drill cuttings,” from the borehole. Solids such as clays, weighting agents, and other additives are incorporated continuously into the mud, with solids-control equipment employed at the rigsite to remove them and return the drilling fluid to the active system in a usable condition. Equipment, such as shakers and centrifuges, are used to remove larger particulate solids. However, as drilling fluids are used to drill multiple holes, fine particles can build up and ultimately create problems for efficient drilling.
Typically, the drilling fluid is diluted and reformulated to reduce the concentration of these fine solids and return the fluid to acceptable physical properties. However, this process is often costly and also increases the volume of drilling fluid, leading to problems of storage, transport, and disposal.
Environmental issues are posed due to contamination of the solids with hydrocarbons, and the need to reuse expensive solid additives. Decanting centrifuges have been developed to deliver high fluid recovery rates and efficient solids control. Centrifuges can recover as much as 95% of the barite in weighted drilling fluids. The barite is returned to the active mud system, while the decanting centrifuge discards the finer, lower-gravity solids.
Centrifuges typically reject solids onto a metal slide, which is usually a U-shaped trough with various struts and reinforcements to mount the trough to the underside of a centrifuge. However, these slides are relatively fragile and subject to rust and damage from normal operation. Further, solids rejected from the centrifuge may stick to the slide, with the need for frequent manual intervention.